Methacrylic ester polymerization



3,030,349 METHACRYLEC ESTER FOLYMERIZATIGN Palmer B. Sticlmey, Columbus,Chic, and Wendeil Overhults, Silver Spring, and Frank X. Werber,Kensington, Md, assignors, by direct and mesne assignments, to W. R.Grace dz (30., New York, N.Y., a corporation of Connecticut N Drawing.Filed May 6, 1960, Ser. No. 27,271 4 Claims. (Cl. 260-895) Thisinvention is concerned with the polymerization of methacrylic esters.More particularly, this invention is directed to polymerizingmethacrylic esters, especially those resulting from the esterificationof methacrylic acid with alkanols and glycols having the generalformula:

wherein n is either 1 or 2 and R is an alkyl or alkalene groupcontaining 1-8 carbon atoms.

It is known that methyl methacrylate can be polymerized in the presenceof aluminum triethyl in a non-polar solvent such as toluene at 0 C. SeeBelgian Patent No. 566,713. Although the resulting polymer obtained bythis method is crystalline and has a melting point in excess of 100 C.,the polymerization rate of the system is slow thereby necessitating longpolymerization periods which detract from the systems commercialacceptability.

Surprisingly, it has now been found possible to increase thepolymerization rate of methacrylic esters of the general formula:

where n is either 1 or 2 and R is an alkyl or alkalene group containing1 to 8 carbon atoms by subjecting said esters in an inert solvent to theaction of an aluminum trialkyl catalyst, in combination with catalyticactivators consisting essentially of an anhydrous halide of a rare earthelement and an amine. The catalyst system of the instant invention givesa polymerization rate in excess of that obtained by an aluminum trialkylcatalyst per se, and also increases the amount of acetone insolublepolymer.

The reason for the increased polymerization rate is not known. It isknown that an anhydrous halide of a rare earth element per se does notpolymerized methyl meth acrylate. It is also known that an anhydroushalide of a rare earth element in combination with an amine does notpolymerize methyl methacrylate. In addition, it is known that aluminumtrialkyl in combination with an amine polymerizes methyl methacrylatebut yields obtained therefrom are less than that obtained when thecatalyst is aluminum trialkyl per se. From the aforesaid disclosures, itcan only be reasoned that the catalyst and catalyst activators combinedhave some unknown synergistic effect which results in the increasedpolymerization rate, as will be shown by the examples hereinafter.Additionally, it is preferred to add the catalyst and catalystactivators to the system prior to the addition of the monomer to bepolymerized. Furthermore, it is necessary that they be added in thefollowing order: rare earth halide, aluminum trialkyl and amine toobtain the optimum results.

In order to show the increased yield of the instant invention over thatobtained by using an aluminum trialkyl per so as a catalyst, apolymerization rate defined herein as being equal to grams polymer gramsaluminum trialkylxreaction time (hrs.) will be used.

The following examples will more clearly explain this 3,930,349 PatentedApr. 17, 1962 ice invention but are not to be deemed as limiting itsscope.

In performing the instant invention, the reaction is carried out under ablanket of an inert atmosphere to insure that the catalyst does notreact with oxygen, moisture or other contaminants which tend todeactivate the catalyst. In the examples stated herein, pure drylampgrade nitrogen is used as the inert atmosphere. However, the noblegases, especially argon and helium are equally suitable.

Example 1 A 500 ml. round bottom flask fitted with stirrer, condenser,thermometer, nitrogen inlet aud neoprene diaphragm for admission ofhypodermic needle was charged in a nitrogen dry-box with 50 ml.n-heptane and 0.003 mole SmCl The flask was removed from the dry box,its contents agitated, and put under a nitrogen blanket through theinlet tube while heat was applied to maintain a temperature of 70 C.therein. The flask was then charged by hypodermic syringe with 0.006mole triethyl aluminum through the neoprene diaphragm followed by ahypodermic charge of 0.003 mole of tri-n-butyl amine. 0.28 mole ofredistilled methyl methacrylate monomer was then added to the flask. Theflask was heated to C. and maintained thereat during the.

polymerization reaction. After 5 hours, the reaction was terminated andmethyl alcohol was added to the flaskto inactivate the catalyst system.The solid methyl methacrylate polymer product was filtered, ground in aWaring Blender with additional methyl alcohol, and dried. The dryproduct weighed 20.1 grams. fluxed in acetone, cooled to roomtemperature, and filtered. The dried acetone-insoluble portion weighed18.1

grams polymer grams aluminum trialkyl reacti0n time (hrs.)

of the acetone insoluble polymer product was 5.3.

The

acetone-soluble polymer product was precipitated from solution withmethyl alcohol, filtered, and dried. The

dry acetone-soluble polymer product weighed 2 grams. The overallpolymerization rate of the system was 5.88.

To point up the increase in polymerization rate ob-' 1 tained by theinstant invention over a system wherein an aluminum trialkyl per se isused as catalyst, as taught by the prior art, the following run wasmade.

Example 2 The equipment andprocedure were the same as in Example 1,except that the catalyst consisted of 0.006

mole triethyl aluminum without any catalyst activators. 0.28 mole ofmethyl methacrylate were charged to the reactor and the reactor washeated from 70 C. to 85 C. After a 5 hour run, the polymerizationreaction was discontinued and the solid methyl methacrylate polymerproduct was separated into acetone soluble and insoluble portions as inExample 1. The dried acetone-insoluble portion weighed 10.5 grams andmelted at a temperature in the range 146-160 C. The polymerization rateof the acetone insoluble polymer product was 3.07, and the overallpolymerization rate was 3.71. A comparison of the polymerization ratesin Examples land 2 show a 50% increase in the overall'polymerizationrate obtained by the practice of this invention.

Example 3 The equipment procedure and proportion of reactants of Example1 was followed except that 0.003 mole of The product was re-.

YbCl was substituted for the 0.003 mole SmCl 11.2 grams ofacetone-insoluble methyl methacrylate polymer product having a meltingpoint in the range of 146460 Was obtained. The polymerization rate forthe acetoneinsoluble polymer was 3.28. The acetone soluble portion (7.1grams) had a polymerization rate of 2.09 thereby giving an overallpolymerization rate of 5.37.

Example 4 The equipment, procedure, and proportion of reactants ofExample 1 was followed except that 0.20 mole ethylene dimethacrylate,i.e.

monomer was substituted for the methyl methacrylate monomer. Theethylene dimethacrylate polymer prodnot was washed with 100 ml. methylalcohol to decompose the catalyst. The solid polymer was filtered,ground in a Waring Blendor, with additional methyl alcohol and dried.The dried polymer product proved acetone insoluble and weighed 19 grams.The polymer product softened at a temperature in excess of 240 C.

The rare earth halides which are operable in the present invention as acatalyst activator include all anhydrous halides of the rare earthelements having atomic numbers 57-71 in the periodic table.

Although the aluminum trialkyl used in all the examples was aluminumtriethyl, the aluminum tri-lower alkyls in general are operative incombination with anhydrous halides of the rare earth elements and aminesto catalyze the polymerization of the methacrylic esters of thepresent'invention. By lower aluminum tri alkyls is meant aluminum alkylshaving 1-8 carbon atoms in the alkyl group.

In addition to the amine specified in the enamples, the following arealso operable:

Methylamine Dimethyl aniline Dimethylamine Pyridine Trimethylamine Gammacolloidine n-Propylamine u-Naphthylamine Di-isopropylamine MelamineQ-ethylhexylamine p-Toluidine Di-n-octylamine N-methylanilineTrioctylamine Diphenylamine Aniline p-Xylidine Triethylarnine c-Phenylenediamine Hexamethylenediamine Benzidine Polymerization ispreferably performed in the presence of a solvent. The solvent used inthe practice of this invention'should be one which is inert and does notinteract with either the monomer to be polymerized, the catalyst,catalyst activator-s, or the growing polymer chain. The preferred inertsolvents are dry aliphatic hydrocarbon solvents in the alkane andcycloalkane groups. Examples of the preferred solvents includen-pentane, nhexane', n-heptane, n-octane, n-nonane, and cyclohexane.

The reaction may be performed under a broad range of temperatures. Sincethe polymerization rate varies directly with temperatures, it ispreferable to use as high a temperature as possible whereat anacetone-insoluble polymer may still be obtained. A temperature range ofminus 45 to plus 150 C. is operable, preferably a temperature in therange -90 C. is employed.

The polymerization reaction is carried out at atmospheric pressure.Higher or lower pressures are operable bu'tare unnecessary.

The amounts of catalyst and catalyst activators are not critical.Relatively small amounts are operable to form relatively large amountsof polymer. In general a practical range is (1001-01 mole of combinedcatalyst and activator per mole of monomer to be polymerized. Evenlarger amounts of combined catalyst and activators are operable butsometimes present a purification problem.

The ratio of the rare earth anhydrous halide to aluminum trialkyl is notcritical, nor is the ratio of amine to either the rare earth anhydroushalide or to the aluminum trialkyl critical. Molar ratios of aluminumtrialkyl:amine:rare earth anhydrous halide of 1:015 to 6:03 to 2 areoperative; the preferred range is respectively 1 :0.3-1:O3-0.5.

The acetone-insoluble polymers produced by the present invention can beused in the same manner and means as the polymers formed by the priorart. Such uses include molded and extruded articles of commerce, e.g.,signs, automotive ornaments, instrument panel parts, refiectors and thelike.

Other monomers of methacrylic esters capable of being polymerized by theinstant invention include t-butyl methacrylate, n-heXyl methacrylate,n-butyl methacrylate, npropyl methacrylate, cyclohexyl methacrylate,isopropyl methacrylate, benzyl methacrylate, phenyl methacrylate,a-naphthyl methacrylate, 1,3-propylene dimethacrylate, 1,8 octylenedimethacrylate, 1,9 nonamethylene dimethacrylate, 1,10 decamethylenedimethacrylate and the like.

We claim:

1. The process of polymerizing a member of the monomer group consistingof methyl methacrylate and ethylene dimethyacrylate which comprisessubjecting the group member to the action of a catalyst consistingessentially of aluminum triethyl in combination with catalyst activatorsconsisting essentially of tri-n-butyl amine and an anhydrous trivalentchloride of a member of the group consisting of samarium and ytterbium.

2. A process of obtaining an acetone insoluble polymethylmethacrylatehaving a melting point in excess of C. which comprises contacting methylmethacrylate in an n-heptane solvent with a catalyst consistingessentially of aluminum triethyl in combination with catalyst activatorsconsisting essentially of tri-n-butyl amine and an anhydrous trivalentchloride of a member of the group consisting of samarium and ytterbium,the mole ratio of the aforesaid catalyst and catalyst activators beingin the range I of 1 :0. l5--6 0.3-2 respectively.

3. The process of obtaining an acetone insoluble ethylene dimethacrylatesolid polymer having a melting point above 240 which comprisescontacting ethylene dimethacrylate in an n-heptane solvent with acatalyst consisting essentially of aluminum triethyl in combination withcatalyst activators consisting essentially of tri-n-butyl amine and ananhydrous trivalent chloride of a member of the group consisting ofSamarium and ytterbiurn, the mole ratio of said catalyst and catalystactivators being in the range 1:0.15-6:0.3-2 respectively.

4. In a process for polymerizing methyl methacrylate in the presence ofa catalyst consisting of an aluminum trialkyl the improvement wherebythe polymerization rate is increased comprising adding catalystactivators consisting essentially of tri-n-butyl amine and an anhydroustrivalent chloride of a member of the group consisting of Samarium andytterbium.

References Cited in the file of this patent UNITED STATES PATENTS2,932,633 Juveland et al Apr. 12, 1960 2,953,586 Hafner et al Sept. 20,1960 FOREIGN PATENTS 833,579 Great Britain Apr. 27, 1960

1. THE PROCESS OF POLYMERIZING A MEMBER OF THE MONOMER GROUP CONSISTINGOF METHYACRYLATE AND ETHYLENE DIMETHYACRYLATE WHICH COMPRISES SUBJECTINGTHE GROUP MEMBER TO THE ACTION OF A CATALYST CONSISTING ESSENTIALLY OFALUMINUM TRIETHYL IN COMBINATION WITH CATALYST ACTIVATORS CONSISTINGESSENTIALLY OF TRI-N-BUTYL AMINE AND AN ANHYDROUS TRIVALENT CHLORIDE OFA MEMBER OF THE GROUP CONSISTING OF SAMARIUM AND YTTERBIUM.